This invention relates to an injection molding machine for synthetic materials and is of the type which has a mold changing device arranged adjacent the mold closing unit of the injection molding machine. The mold closing unit comprises a clamping assembly for clamping the mold halves of the injection mold assembly to and releasing them from the mold carriers. Each mold half is provided, on its rear side, with an engagement plate (clamping plate) to be directly contacted by the mold closing unit. The mold changing device includes a conveying mechanism for a transverse shifting of the injection mold assembly into and out of the working position in the mold closing unit.
The mold assembly (formed of the two mold halves) has a bolting device to firmly interlock the mold halves to one another to ensure that they behave as a single component during handling of the mold assembly externally of the injection molding machine, for example, during periods of mold assembly replacement. The bolting device has at least one two-arm angle lever (hereafter also referred to as a bell crank lever) which is articulated for pivotal motion to one of the mold halves. The bell crank lever is conventionally swung by a motorized unbolting drive against the force of a return spring into the releasing (unbolted) position. The bell crank lever may be pivoted into its bolting (interlocking) position by the biased return spring.
In a known injection mold changing device as disclosed, for example, in U.S. Pat. No. 4,555,228, separate hydraulic actuating cylinders are provided at the rear side of the stationary mold carrier for operating two bell crank levers arranged at the vertical lateral faces of one of the mold halves. In this arrangement, an unbolting of the two mold halves from one another is feasible only after the mold half carrying the bell crank levers is clamped to the stationary mold carrier by means of clamping cylinders provided particularly for this purpose.
As disclosed, for example, in U.S. Pat. No. 4,671,764, it is also known to utilize the approach of one of the mold halves towards the adjacent mold carrier as a signal for unbolting the mold halves of the injection mold assembly from one another. The bolting components are constituted by coupling pins which are axially shiftably supported in centering bodies of the injection mold assembly and which, under the effect of the pressure of a biased spring, project rearwardly from the bolted injection mold assembly. By virtue of this arrangement it is achieved that upon removal of the mold halves (which receive the centering bodies) from the associated mold carriers, there is effected a mutual bolting and, upon clamping these mold halves on the mold carriers, there is effected an unbolting (release) of the two mold halves from one another in an automatic manner.
It is further known to utilize the closing and opening motion of the mold closing unit for actuating the bolting mechanism for the mold halves, as disclosed, for example, in United Kingdom Pat. No. 2,067,458.
Mold changing devices are also known wherein the injection mold assembly is movable into and out of the mold clamping space on a horizontal conveyor track oriented perpendicularly to the mold closing direction. During such conveyance the injection mold assembly is supported and guided by both mold carriers. In this arrangement, the engagement faces of the clamping plates of the mold halves are at a minimal distance from the adjacent clamping faces of the mold carriers. Such an arrangement is disclosed, for example, in U.S. Pat. No. 4,462,783. It is further known to utilize pivotal bolting shackles for a bilateral manual bolting of an injection mold assembly as disclosed, for example, in German Utility Model No. 8,212,045.5.